System and method for controlling air temperature in an appliance

ABSTRACT

An apparatus and method for controlling air temperature in an appliance. The apparatus includes an air cooling unit disposed in an airflow path and an air heating unit disposed in the airflow path and fluidically coupled to the air cooling unit by a refrigerant. The apparatus also includes a de-heater fluidically coupled to the air cooling unit and the air heating unit by the refrigerant to controllably dissipate heat from the refrigerant.

BACKGROUND

Embodiments of the present invention relate to a system and method for controlling air temperature in an appliance.

Traditionally, hot air has been used in one form or another in clothes dryers to dry articles placed in a drying compartment such as a drum. In one conventional arrangement, air is heated via a heating element and fed by a fan into the drum where it interfaces with the articles to be dried. Moisture contained by the wet articles is then evaporated by the hot dry air, which in turn is vented out of the dryer. Although such drying systems may well dry the articles, they are very inefficient and provide little control over the air temperature to which the articles are exposed.

Another arrangement for drying includes the use of a heat pump, whereby heating and cooling units are connected at various points in an airflow path to facilitate article drying. However, in conventional heat pump arrangements, operation of a compressor is modulated on and off to control heating and cooling of the airflow. This also tends to be inefficient and provides little control over the air temperature to which the articles are exposed.

As it is common for a wide variety of cleaning solutions, solvents and materials to be used when drying articles, it is often desirable to keep the air temperatures within a drum of the drying apparatus either within a particular temperature range or below a particular maximum threshold temperature. Unfortunately, current drying systems either do not provide this capability or attempt do so at the cost of efficiency.

BRIEF DESCRIPTION

Briefly, in accordance with one embodiment of the invention, there is provided an apparatus including an air cooling unit disposed in an airflow path and an air heating unit disposed in the airflow path and fluidically coupled to the air cooling unit by a refrigerant. The apparatus also includes a de-heater fluidically coupled to the air cooling unit and the air heating unit by the refrigerant to controllably dissipate heat from the refrigerant.

In accordance with another embodiment of the invention, there is provided a method for controlling air temperature in an appliance. The method includes disposing an air cooling unit in an airflow path designed to carry an airflow, disposing an air heating unit in the airflow path and fluidically coupling the air heating unit to the air cooling unit by a refrigerant. The method also includes fluidically coupling a de-heater and the de-heater to the air cooling unit and the air heating unit by the refrigerant to controllably dissipate heat from the refrigerant.

DRAWINGS

FIG. 1 is a block diagram of a thermal management system for controlling air temperature in an appliance in accordance with one embodiment of the invention.

FIG. 2 is a block diagram of a thermal management system equipped with a controller for controlling air temperature in an appliance in accordance with a further embodiment of the invention.

FIG. 3 is a block diagram illustrating operational aspects of the thermal management system of FIG. 2 equipped with a controller for controlling air temperature in an appliance in accordance with an example embodiment.

FIG. 4 is a graphical representation illustrating an example functional relationship between air temperature and refrigerant temperature in an appliance incorporated with one or more embodiments of the invention;

FIG. 5 is a flow chart illustrating a methodology for monitoring temperature within an appliance in accordance with one embodiment of the invention; and

FIG. 6 illustrates an operational flow of a thermal management system for controlling air temperature in an appliance in accordance with one embodiment of the invention.

DETAILED DESCRIPTION

As will be described in further detail herein, embodiments of the present invention include a system and method for thermal management of an airflow within an appliance. In certain embodiments, the thermal management system described herein may be incorporated within a variety of appliances such as article cleaning apparatuses including but not limited to a washing machine, a dryer, and a combination washer/dryer system (hereinafter referred to as “cleaning apparatuses”). The term “article” as used herein is intended to refer to a broad class of items such as fabrics, textiles, garments, linens, and any other items or material that may be cleaned or dried in a home or commercial based washing, drying and/or dry-cleaning machine.

FIG. 1 illustrates one embodiment of a system incorporating teachings of the present invention. In the illustrated embodiment, the components of the thermal management system 10 are arranged in such a manner so as to limit or otherwise control the temperature of an airflow to which articles within an article holding drum (hereinafter “drum”) 24 may be exposed. As shown in FIG. 1, the illustrated thermal management system 10 includes an air-heating unit 16, an air-cooling unit 18, a compressor 12 and a de-heater 14 fluidically coupled by a refrigerant along a refrigerant flow path 4.

Refrigerant flow path 4 represents an arrangement within which a refrigeration liquid or material (hereinafter “refrigerant”) may be circulated in a closed loop between components of the thermal management system 10. In one embodiment, the refrigerant may be fluorocarbon R-22, however in other embodiments other refrigerants may be used.

The air-heating unit 16 and the air-cooling unit 18 are further arranged in an airflow path 2, which carries an airflow generated by a blower 22. In the illustrated embodiment, the airflow generated by blower 22 circulates within the system 10 such that the airflow contacts the air-cooling unit 18 and the air-heating unit 16 as it flows toward the drum 24. The drum 24 may be an article drying drum, washing drum or combination washing/drying drum for example. Moreover, drum 24 may be an integral part of the thermal management system 10 or part of a cleaning apparatus to which the thermal management system 10 is incorporated. In one embodiment, the air-heating unit 16 may be a condenser and the air-cooling unit 18 may be a evaporator.

In accordance with one embodiment of the invention, the system 10 facilitates the exchange of heat between an airflow (e.g., as indicated by airflow path 2), and the refrigerant (e.g., as indicated by refrigerant flow path 4). In operation, the airflow generated by blower 22 contacts the cooling unit 18 where the airflow is cooled by relatively colder refrigerant flowing through the cooling unit 18. As the airflow is cooled, moisture present within the airflow condenses out of the airflow, which may in turn be recycled or discarded. After passing the cooling unit 18, the cooled air contacts the heating unit 16 where the airflow is heated by relatively warmer refrigerant flowing through the heating unit 16. The heated airflow is then directed to the drum 24, which contains the articles to be dried. As the relatively hot dry airflow is mixed with wet articles present within the drum 24, it absorbs moisture from the wet articles in the drum 24. The moisture-containing airflow is then returned to the cooling unit 18 where the heating and cooling process repeats. Although a single blower 22 is illustrated in FIG. 1, additional blowers 22 may be positioned at more than one point along the airflow path 2 to facilitate movement of the airflow around the cleaning apparatus. In one embodiment, blower 22 is a fan, however other air movement mechanisms may be used.

As was mentioned above, in order to heat and cool the airflow as described, refrigerant is circulated along the refrigerant flow path 4. Since the refrigerant flow path 4 represents a closed loop, the beginning and end of the refrigerant flow can be considered arbitrary designations for the purpose of this description. For the purposes of simplicity, the following description assumes an operational starting point corresponding to the cooling unit 18.

At the cooling unit 18, the relatively cool refrigerant absorbs heat from the relatively warmer airflow causing the airflow to be cooled and the refrigerant to be converted from a liquid phase to a gas phase. The refrigerant then proceeds to the compressor 12 where it is compressed causing the refrigerant to be heated and become a hot, high-pressure gas. Without any additional modifications, the relatively hot refrigerant could then be passed through the heating unit 16 where heat from the refrigerant would be given off to the relatively cooler airflow causing the airflow to be heated. The compressed refrigerant could then be provided to an expansion chamber 28 allowing the compressed refrigerant to expand and thereby be cooled once again. Control of the air temperature within such a system, however would be dependent upon the switching “on” and “off”of the compressor 12. A method of controlling airflow temperature based on switching on/off of the compressor 12 however puts operational limits on the efficiency of the thermal management system. For example, every time a compressor is switched off, a prescribed delay is required before it can be switched on again. During this time, the air loses additional heat and as such, may thereby adversely affect the precision and efficiency of temperature control. Moreover, the operability and reliability of the compressor may be affected owing to frequent on/off cycles.

In certain cleaning apparatuses however, it may be important or otherwise desirable to more precisely and efficiently control the temperature of the air to which articles in the drum 24 are to be exposed. For example, in cleaning apparatuses that utilize certain wash liquors or solvents having known flashpoints, it may be desirable to keep airflow temperatures within the drum 24 from reaching or exceeding such flashpoint temperatures. In accordance with one embodiment of the present invention and as illustrated in FIG. 1, de-heater 14 is advantageously provided to facilitate controllable temperature regulation of the refrigerant that in turn operates to regulate the temperature of the airflow. In particular, the operation of de-heater 14 facilitates air temperature regulation within the drum 24. Incorporation of the de-heater 14 into the refrigerant flow path 4 of the thermal management system 10 facilitates continuous operation of the system without having to switch the compressor 12 “on” and “off”, thereby enhancing energy efficiency associated with operating a cleaning apparatus incorporating the thermal management system 10. In a further embodiment of the present invention, the de-heater 14 may be utilized to assist the heating unit 16 in heating the air stream prior to its entering the drum 24. In one embodiment of the invention, the de-heater 14 may be a fin and tube type heat exchanger. In another embodiment of the invention, the de-heater 14 may be a tube and tube type heat exchanger.

FIG. 2 is a block diagram of a thermal management system 20 equipped with a controller for controlling air temperature in an appliance in accordance with a further embodiment of the invention. The thermal management system 20 is similar in form to the thermal management system 10 of FIG. 1 but has been further enhanced by the addition of a bypass airflow path 6, a controller 32 and a number of sensors to measure the temperatures at different points of the airflow path 2.

In one embodiment, the bypass airflow path 6 includes a bypass valve 36 to bypass at least a portion of the airflow around the cooling unit 18. In the illustrated embodiment, the sensors in the system 20 include a de-heater outlet sensor 34 positioned at the outlet of the de-heater 14 to measure or otherwise sense the refrigerant temperature, a cooling outlet sensor 38 positioned at the outlet of the cooling unit 18 to measure or otherwise sense the air temperature at the outlet of the cooling unit 18, and a drum inlet sensor 42 positioned at the inlet of the drum 24 to measure or otherwise sense the air temperature at the inlet of the drum 24. In one embodiment, one or more of sensors 34, 38 and 42 may be a thermocouple.

In general, the controller 32 is employed to control the exchange of the heat between the airflow following airflow path 2 and the refrigerant following the refrigerant flow path 4. More specifically, depending on the temperatures at various sensing points on the airflow path 2 and the refrigerant flow path 4 as explained above, the controller 32 monitors and controls operation of the bypass valve 36, the blower 22, and the de-heater 14 such that a number of operating conditions are typically at preferred levels during a typical operation cycle of the system 20.

For example, in one embodiment of the invention the de-heater 14 is equipped with a blower or air-moving device such as a fan 26 that is controlled by the controller 32 to remove super heat from the hot compressed refrigerant passing through the de-heater 14 along refrigerant flow path 4. As the fan 26 operates to increases airflow across the de-heater 14 in response to an indication received from the controller 32, heat exchange between the refrigerant and the ambient is increased. In one embodiment, heated air resulting from the heat exchange at de-heater 14 may be directed to the drum 24 to further increase the air temperature and drying capability within the drum 24.

In another example, if the temperature of the airflow within the drum 24 (e.g., as may be determined by sensor 42) needs to be increased, the controller 32 may regulate the opening of the bypass valve 36 so that extra amount of bypass airflow is diverted into the bypass flow path 6. If the inlet stream is not close to being saturated then additional thermal capacity can be gained since the heating unit 16 is not required to reheat that portion of the airflow that bypasses the cooling unit 18. If necessary, the controller 32 may also regulate the speed of the blower 22 so that a varying amount of airflow is taken into airflow path 2 to achieve a desired air temperature.

In one embodiment, the controller 32 determines and interprets aspects of the heat exchange of the thermal management system 20 in accordance with a determined criterion. For instance, in one embodiment, the determined criterion may include a binary comparison of the temperature of the thermal management system 20 with a determined reference value of temperature. In another embodiment, the determined criterion may comprise a comparison between a temperature within the thermal management system 20 and a determined maximum allowable temperature. In yet another embodiment, the determined criterion may comprise a comparison between a temperature within the thermal management system 20 and a determined minimum value for the same temperature.

However the criterion for comparison may be selected, if the sensed heating or cooling requirement of the airflow or the refrigerant in the thermal management system 20 falls outside of a determined reference range for example, the controller 32 may determine that the status of the heat exchange is not acceptable and additional action may then be identified. In that event, the controller 32 may perform a variety of operations to achieve a desired thermal state within the cleaning apparatus.

Structurally, the controller 32 may comprise a micro-controller or a solid-state switch configured for communication with the sensors 34, 38 and 42 and communication with the fan 26, the blower 22 and the flow control valve 36. The communication with the controller 32 may take place using the signal line 56 coupled to the de-heater outlet sensor 34, signal line 58 coupled to the drum inlet sensor 42 and signal line 62 coupled to the air cooler outlet sensor 38. In a like manner, communication from the controller 32 may take place using signal line 52 coupled to the blower 22, signal line 54 coupled to the de-heater fan 26 and signal line 55 coupled to the bypass flow control valve 36. In one embodiment, the controller 32 comprises an analog-to-digital converter accessible through one or more analog input ports. In another embodiment, the controller 32 may include read-out displays, read-only memory, random access memory, and a conventional data bus.

As will be appreciated, the controller 32 may be embodied in several other ways. In one embodiment, the controller 32 may include a logical processor, threshold detection circuitry and/or an alerting system. Typically, the logical processor is a processing unit that performs computing tasks. It may be a software construct made up using software application programs or operating system resources. In other instances, it may also be simulated by one or more physical processor(s) performing scheduling of processing tasks for more than one single thread of execution thereby simulating more than one physical processing unit. The controller 32 aids the threshold detection circuitry in estimating the strength a typical temperature parameter. For instance, the temperature parameter may include de-heater outlet temperature, or drum inlet temperature or evaporator outlet temperature. Further, the controller 32 may determine the strength of the signals from such temperature parameters. This estimate information may be reported to a remote control unit or to an alerting system.

EXAMPLE OPERATION

FIG. 3 is a block diagram of a thermal management system 30 equipped with a controller for controlling air temperature in an appliance in accordance with an example embodiment. The thermal management system 30 is similar in form to the thermal management system 20 of FIG. 2 except for the addition of example operational parameters associated with operation of the thermal management system within a cleaning apparatus. Such operational parameters include specific temperatures or temperature ranges of air at various inlet and outlet points of various components positioned in the airflow path 2, as well as flow rates of air in both the main airflow path 2 and in the bypass airflow path 6. The operational parameters also include specific temperatures or temperature ranges of the refrigerant at various inlet and outlet points of various components positioned on the refrigerant flow path.

In the example embodiment of FIG. 3, a typical volume flow rate of air in the main stream (e.g., that airflow which follows airflow path 2) is 240 cubic feet per minute (cfm) whereas a typical volume flow rate for air in the bypass stream (e.g., that airflow which follows bypass airflow path 6) comprises 29% of the volume flow rate of air in the main stream (e.g., 69.6 cfm). Moreover as shown, when the inlet air temperature at the evaporator 18 is typically within a range of 124 F to 129 F, the outlet air temperature at the evaporator 18 is typically at about 68 F. In a like manner, when the inlet air temperature at the condenser 16 is typically within a range of 84 F to 86 F, then the outlet air temperature at the condenser 16 is typically at about 139 F. This results in an inlet air temperature at the drum 24 that can be typically at about 139 F. In turn, and the outlet air temperature at the drum 24 can be typically within a range of 124 F-129 F.

Continuing to refer to the example embodiment of FIG. 3, when a typical inlet temperature of the refrigerant at the compressor 12 is typically at about 42 F, the outlet temperature of the refrigerant at the compressor 12 is typically within a range of about 180 F-220 F. In turn, if the inlet temperature of the refrigerant at the de-heater 14 is typically within a range of about 180 F-220 F then due at least in part upon the operation of the de-heater 14 in combination with the fan 26, the outlet temperature of the refrigerant at the de-heater 14 is typically at about 140 F. In the example embodiment, the inlet and outlet temperatures of the refrigerant at the condenser 16 is typically at the condensing temperature of the particular refrigerant used in the particular cleaning apparatus. Further, if the inlet temperature of the refrigerant at the expansion chamber 28 is typically at about 140 F, the outlet temperature of the refrigerant at the expansion chamber 28 is typically at about 42 F. The inlet and outlet temperatures of the refrigerant at the evaporator 18 can then further be typically at the evaporating temperature of the particular refrigerant used in the particular cleaning apparatus. In one embodiment, the refrigerant used is R-22.

The numerical values of the temperatures, temperature ranges, the flow rate of the air in the main stream and the flow rate of the air in the bypassed stream are provided for the purpose of illustration and these values are specific to one exemplary design of the apparatus of FIG. 3. As such, the thermal management system 10 or 20 illustrated in relation to FIG. 1 or FIG. 2 should not be construed to be limited by the illustrated values in the thermal management system 30 illustrated in FIG. 3.

In another embodiment of the invention, the operation of the cleaning apparatus of FIG. 2 may be enhanced by using a wash liquid that contains solvents such as cyclic siloxane (scientifically known as Decca Methyl Cyclo Penta Siloxane) or D5 in a washing cycle of the cleaning apparatus as the cleaning quality can be improved with the use of such solvents. However, one of the challenging constraints associated with use of such solvents is flammability of the solvents. Federal guidelines for commercial dry-cleaning systems as listed by National Fire Protection Association (NFPA) 32 and as recommended in association with the use cyclic siloxane or D5, classify the solvent as a Class IIIA solvent based on its flammability point of 170 F. NFPA 32 guidelines for safe operation of D5 based laundry systems requires that the temperature everywhere in the associated appliance or system is 30 F below the flash point temperature (e.g., less than 140 F for D5). As illustrated above, in the thermal management system 20 of FIG. 2, thermocouples and other sensitive sensors are used in various points in the airflow to monitor and facilitate control of the air temperature and such that the air temperature is kept well below 140F. Thus, through the incorporation of embodiments of the present invention, the apparatus of FIG. 2 is well equipped to meet the demand of a high quality cleaning apparatus using cyclic siloxane or D5 solvent based wash liquid.

FIG. 4 is a graphical representation 40 of an example functional relationship between air temperature and refrigerant temperature in an appliance and time length of operation of the appliance in accordance with an embodiment of the invention. Referring to FIG. 4, each curve illustrates an example of dynamic temperature changes of either the air or of the refrigerant used in a washing machine for the inlet or outlet conditions common to washing machine applications. The vertical or the Y-axis 72 of the temperature-time curves represents temperature values expressed in degree Fahrenheit and the horizontal or the X-axis 74 represents time interval values recorded from the start of the cleaning apparatus as expressed in seconds. Three different temperature curves 76, 78 and 82 are presented for illustrative purposes. Curve 76 represents the temperature of the refrigerant at the outlet of the condenser 16, curve 78 represents the temperature of the refrigerant at the inlet of the condenser 16 and curve 82 represents the temperature of air at the outlet of the condenser 16.

Referring to FIG. 4, it will be noted that by using the de-heater 14 in tandem with the condenser 16, the temperature of the refrigerant at the inlet of the condenser 16 is constrained within a controlled limit. In one embodiment of the invention, the de-heater 14 operates to maintain the refrigerant at a steady temperature while the refrigerant condenses in the condenser 16. In the illustrated example of FIG. 4, the steady temperature may be 130 degrees Fahrenheit, which is the condensation temperature of the R-22 refrigerant that happens to have been used. The oscillations in the curves 76 and 78 represent the rise or fall of the temperature of the refrigerant due to the variation in the speed of the fan 26 of FIG. 2 as is relates to the operation of the de-heater 14. This functionality will be described in more details later in relation to FIG. 6. The heat given up by the refrigerant during its condensation in the condenser 16 is absorbed by the airflow and the temperature of the airflow in turn rises from room temperature up to a steady temperature over a period of time. The steady temperature of the airflow in the particular example of FIG. 4 may be 110 degree Fahrenheit, depending on the thermal efficiency of the apparatus and its components, which has been determined to be a preferred temperature for drying clothes in the drum 24.

FIG. 5 illustrates a methodology for monitoring and controlling temperature within an appliance in accordance with one embodiment of the invention. The method 50 begins with an airflow path being defined to carry an airflow for drying articles within the appliance as in functional block 102. At the same time a refrigerant flow path is defined to circulate a refrigerant in a closed loop such that the refrigerant acts at least in part to both heat and cool the airflow as in functional block 104. Lastly, the temperature of the refrigerant is then controlled such that the airflow does not exceed a determined temperature as in functional block 106.

FIG. 6 illustrates an operational flow of the thermal management system 30 of FIG. 2 for controlling air temperature in an appliance in accordance with an exemplary embodiment of the invention. As illustrated, description of the operational flow begins at functional block 108. Thereafter, the controller 32 performs a number of operations, which may be performed in parallel or in a sequential order. However, for the purposes of illustration, it is assumed that the operations illustrated in FIG. 6 occur in parallel. In particular, the temperature of the refrigerant in refrigerant flow path 4 is sensed at an outlet end of the de-heater 14 (functional block 114) and the decision logic of the controller 32 then determines whether the sensed temperature of the refrigerant is less than a determined set point (functional block 122). In one embodiment, the temperature of the refrigerant is sensed using a thermocouple positioned at the outlet end of the de-heater 14. If the temperature of the refrigerant is determined to be lower than the determined set point, the speed of the fan 26 associated with de-heater 14 may then be decreased as shown in functional block 124. On the other hand, if the temperature of the refrigerant is determined to be higher than the determined set point, then the fan speed may be increased as shown in functional block 126.

At functional block 116, the controller 32 further identifies the temperature of the air at the inlet of the drum 24 and the decision logic of the controller 32 determines whether the temperature of the air at the inlet of the drum 24 is lower than a determined set point (functional block 132). If the temperature of the air is determined to be higher than the set point, the speed of blower 22 may be increased as shown by functional block 134. On the other hand, if the temperature of the air is determined to be less than the set point, the blower speed is decreased as shown in functional block 136.

At functional block 118, the controller 32 further determines the temperature of the air at the outlet of the evaporator 18 (functional block 118) and the decision logic of the controller 32 determines whether the temperature of the air is less than a determined set point as shown in functional block 142. If the temperature of the air is determined to be higher than the set point, the volume of air that is bypassed around the cooling unit 18 is increased as shown in functional block 144. On the other hand, if the temperature of the air is determined to be less than the set point, the volume of bypassed air is decreased as shown in functional block 146. Finally, in an iterative manner, the decision logic of the controller 32 determines at functional block 152 whether an end of the drying process is reached. If the end of the process is reached, the process completes at functional block 154. Otherwise, the drying process continues to operate accordingly.

Although the present invention has been described with reference to particular embodiments, it should be recognized that these embodiments are merely illustrative of the principles of the present invention. Those of ordinary skill in the art will appreciate that the method of the present invention may be implemented in other ways and embodiments. Accordingly, the description herein should not be read as limiting the present invention, as other embodiments also fall within the scope of the present invention.

While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention. 

1. An apparatus comprising: an air cooling unit disposed in an airflow path; an air heating unit disposed in the airflow path and fluidically coupled to the air cooling unit by a refrigerant; and a de-heater fluidically coupled to the air cooling unit and the air heating unit by the refrigerant to controllably dissipate heat from the refrigerant.
 2. The apparatus of claim 1, wherein the heat is controllably dissipated from the refrigerant such that an airflow following the airflow path is prevented from exceeding a determined temperature.
 3. The apparatus of claim 1, wherein the apparatus further comprises: a blower to generate an airflow along the airflow path; and a drum to contain at least one article for drying, the drum positioned to receive the airflow.
 4. The apparatus of claim 3 further comprising a controller coupled to the air cooling unit, the air heating unit and the de-heater to control an exchange of heat between the airflow and the refrigerant.
 5. The apparatus of claim 4, wherein the apparatus further comprises a first air sensor positioned at an inlet of the drum to sense air temperature at the inlet of the drum and configured to send a signal indicative of the air temperature at the inlet of the drum to the controller.
 6. The apparatus of claim 4 further comprising a bypass valve to cause at least a portion of the airflow to controllably bypass the air cooling unit.
 7. The apparatus of claim 4, wherein the apparatus further comprises a second air sensor positioned at an outlet of the air cooling unit to sense air temperature at the outlet of the air cooling unit and configured to send a signal indicative of the air temperature at the outlet of the air cooling unit to the controller.
 8. The apparatus of claim 4, further comprising: a compressor fluidically coupled to the air cooling unit, the air heating unit, and the de-heater to compress the refrigerant; and an expansion chamber fluidically coupled to the air heating unit to receive the refrigerant from the air heating unit to provide expansion and cooling of the refrigerant.
 9. The apparatus of claim 8, wherein the air heating unit comprises a condenser fluidically coupled to the de-heater to receive the refrigerant exiting from the de-heater, the condenser further in thermal connection with the airflow to transfer heat from the refrigerant to the airflow; and wherein the air cooling unit is an evaporator fluidically coupled between the compressor and the expansion chamber to receive the refrigerant exiting from the expansion chamber, the evaporator further in thermal connection with the airflow to transfer the heat from the airflow to the refrigerant, wherein the refrigerant exiting from the evaporator is circulated back to the compressor.
 10. The apparatus of claim 9 further comprising a fan coupled to the de-heater to provide a second airflow to cool refrigerant passing through the de-heater.
 11. The apparatus of claim 10, wherein operation of the fan is controlled by the controller such that the compressor can operate continuously during heat dissipation from the refrigerant.
 12. The apparatus of claim 11, further comprising a thermocouple positioned at an outlet of the de-heater to sense temperature of the refrigerant at the outlet of the de-heater and configured to send a signal indicative of the temperature of the refrigerant at the outlet to the controller.
 13. A method for controlling air temperature in an appliance, the method comprising: disposing an air cooling unit in an airflow path designed to carry an airflow; disposing an air heating unit in the airflow path and fluidically coupling the air heating unit to the air cooling unit by a refrigerant; and disposing a de-heater and fluidically coupling the de-heater to the air cooling unit and the air heating unit by the refrigerant to controllably dissipate heat from the refrigerant.
 14. The method of claim 13, wherein the heat is controllably dissipated based at least in part upon a temperature of the refrigerant.
 15. The method of claim 13 further comprising: in the air heating unit, transferring heat from the refrigerant to the airflow to heat the airflow; and in the air cooling unit, transferring heat from the airflow to the refrigerant to cool the airflow, wherein the refrigerant exiting from the air cooling unit is compressed to further heat the refrigerant.
 16. In an appliance, a method comprising: defining an airflow path to carry an airflow for drying articles within the appliance; defining a refrigerant flow path to circulate a refrigerant in a closed loop such that the refrigerant acts at least in part to both heat and cool the airflow; and controlling temperature of the refrigerant such that the airflow does not exceed a determined temperature.
 17. The method of claim 16 further comprising: generating the airflow; removing heat from the airflow to create a cooled airflow by exposing the airflow to the refrigerant having a first state; adding a controlled amount of heat to the cooled airflow to create a heated airflow by exposing the cooled airflow to the refrigerant in a second state; and providing the heated airflow to the articles in the appliance.
 18. The method of claim 17 further comprising: cooling the refrigerant to a first temperature; flowing the refrigerant through an evaporator positioned in the airflow path to cool the airflow; heating the refrigerant to a temperature that does not exceed the determined temperature; and flowing the heated refrigerant through a condenser to heat the airflow.
 19. The method of claim 18, wherein heating the refrigerant to a temperature that does not to exceed the determined temperature comprises: compressing the refrigerant; flowing the heated refrigerant through a second condenser; determining whether the temperature of the heated refrigerant is equal to or exceeds the determined temperature; and controllably generating a secondary airflow and directing the secondary airflow toward the second condenser to remove heat from the refrigerant when the temperature of the heated refrigerant is equal to or exceeds the determined temperature.
 20. The method of claim 19, wherein cooling the refrigerant comprises allowing the compressed refrigerant to expand in volume.
 21. The method of claim 19, wherein the second condenser operates to remove super heat from the refrigerant. 